The invention relates to a surgical stapling instrument, which can be used for applying surgical staples or clips to tissue and in particular for performing an anastomosis.
Generally, in the performance of a surgical anastomotic stapling operation, two pieces of lumen or tubular tissue, e.g., intestinal tissue, are attached together by a closed row of staples. In performing the anastomosis with a surgical stapling instrument, the two pieces of tubular tissue are clamped together between an anvil provided with an array of staple forming grooves and a staple holder or cartridge device provided with a plurality of staple receiving slots arranged in a closed row or array in which the staples are received. A staple pusher is advanced to drive the staples into the tissue and form the staples against the anvil. Moreover, a circular knife is advanced to cut the excess tissue clamped between the anvil and the staple holder. As a result, the donut-shaped section of tissue is severed from each lumen and remains on the anvil shaft. The tubular tissue joined by the closed row of staples is unclamped by moving the anvil relative to the staple holder, usually by advancing the anvil shaft distally to move the anvil away from the staple holder. The stapling instrument is removed by pulling the anvil through the opening between the pieces of tubular tissue attached by the array of staples.
Surgical stapling instruments of this kind are well-known. For example, U.S. Pat. No. 5,205,459 describes such an instrument in detail. As usual, the closed row of staples of the instrument disclosed has a planar, circular shape. U.S. Pat. No. 5,275,322 is a document showing a basic version of a circular stapling instrument.
Although the use of the known surgical stapling instruments is very beneficial and greatly facilitates the performance of an anastomosis, it involves some problems. Often it is difficult to retract the instrument from the site of the operation, because it is difficult to move the anvil through the opening bordered by the closed row of staples, which is somewhat stiff. Moreover, after the operation, the incidence of clinical stenosis at the site of the anastomosis is not rare.
In order to overcome these problems, it is proposed in WO 01/54594 A1 to arrange the closed row of staples in a wavy shape which leaves a plane perpendicular to the longitudinal axis of the instrument. In this way, the line along which the staples of the closed row are arranged has a larger total length than the projection of this line onto a plane. Consequently, the length of an anastomosis seam is larger than that of an anastomosis performed by means of conventional stapling instrument. Because of this increased length, the anastomotic site can assume a larger diameter and is more flexible, so that the anvil can be easily moved through the opening created by the knife, and the surgical stapling instrument can be retracted at the end of the surgery more easily. Additionally, the resulting larger anastomosis lumen will alleviate the incidence of clinical complications. On the other hand, if it is sufficient that the total length of the closed row of staples is comparable to that provided by a conventional stapling instrument, this instrument can be designed in a more compact size such that it can be easier inserted into a tubular organ and removed therefrom.
For optimum performance of the stapling instrument disclosed in WO 01/54594 A1, the individual staples are expelled from the cartridge device in a direction perpendicular to the local slope of the wavy shape, which generally is not parallel to the longitudinal axis of the instrument. This requires a more complicated staple drive mechanism which experiences load components transverse to the longitudinal axis of the instrument. Moreover, the alignment of the staple-forming grooves at the anvil to the pointed ends of the staples exiting from the cartridge device is only correct for a certain distance between the cartridge device and the anvil, i.e. for a certain thickness of the tissue clamped between the cartridge device and the anvil, which results in a loss of variability with respect to the tissue thickness.
EP 1 090 592 A1 discloses a linear surgical stapler, in which the anvil has two staple-forming surfaces which are spaced with respect to each other in the staple expelling direction. In this way, the anvil is formed with a stiffening rib which generally strengthens the cantilever design of the linear stapler.